Vein filter

ABSTRACT

A vessel filter comprising a first region and a second region wherein the filter is movable between a collapsed position for delivery to the vessel and an expanded position for placement within the vessel. A first region has a filter portion having a converging region at a first end portion to direct particles toward the center of the filter and the second region is flared in the expanded position to have a transverse dimension increasing toward a second end portion opposite the first end portion. The second region includes a vessel engaging portion at the second end portion. The second region includes a plurality of spaced apart struts with adjacent struts being joined.

This application is a continuation of application Ser. No. 10/805,796,filed on Mar. 22, 2004, now U.S. Pat. No. 7,338,512, which claimspriority from provisional application Ser. No. 60/538,379, filed Jan.22, 2004. The entire contents of both applications are incorporatedherein by reference.

BACKGROUND

1. Technical Field

This application relates to a vascular filter and more particularly to avein filter for capturing blood clots within the vessel.

2. Background of Related Art

Passage of blood clots to the lungs is known as pulmonary embolism.These clots typically originate in the veins of the lower limbs and canmigrate through the vascular system to the lungs where they can obstructblood flow and therefore interfere with oxygenation of the blood.Pulmonary embolisms can also cause shock and even death.

In some instances, blood thinning medication, e.g. anticoagulants suchas Heparin, or sodium warfarin can be given to the patient. Thesemedications, however, have limited use since they may not be able to beadministered to patients after surgery or stroke or given to patientswith high risk of internal bleeding. Also, this medication approach isnot always effective in preventing recurring blood clots.

Therefore, surgical methods to reduce the likelihood of such pulmonaryembolisms by actually blocking the blood clot from reaching the lungshave been developed. One surgical method of treatment involved majorsurgery where the size of the vessel lumen was restricted by placementof ligatures or clips around the vein, e.g. the inferior vena cava whichtransports blood from the lower portion of the body to the heart andlungs. This prevented passage of dangerously large blood clots throughthe vein to the lungs. However, this approach is an invasive surgicalprocedure, requiring an abdominal incision and general anesthesia andfrequently causing vessel thrombosis and lower extremity swelling. Also,there is a lengthy patient recovery time and additional hospital andsurgeon expenses associated with this major surgery. In fact,oftentimes, the patients requiring the surgery are unhealthy and themajor surgery and general anesthesia poses a risk in and of itself.

To avoid such invasive surgery, less invasive surgical techniques havebeen developed. These involve the placement of a mechanical barrier inthe inferior vena cava. These barriers are in the form of filters andare typically inserted through either the femoral vein in the patient'sleg or the right jugular vein in the patient's neck or arm under localanesthesia. The filters are then advanced intravascularly to theinferior vena cava where they are expanded to block migration of theblood clots from the lower portion of the body to the heart and lungs.

These prior filters take various forms. One type of filter is composedof coiled wires such as disclosed in U.S. Pat. Nos. 5,893,869 and6,059,825. Another type of filter consists of legs with free ends havinganchors for embedding in the vessel wall to hold the filter. Thesefilters are disclosed, for example, in U.S. Pat. Nos. 4,688,553,4,781,173, 4,832,055, and 5,059,205, 5,984,947 and 6,007,558. Anothertype of filter is disclosed in U.S. Pat. No. 6,214,025 consisting ofwires twisted together to form a cylindrical anchoring portionconforming to the inner vessel wall surface to exert a radial force anda conical filtering portion.

Several factors have to be considered in designing vein filters. Onefactor is that the filter needs to be securely anchored within thevessel wall, while avoiding traumatic engagement and damage to the wallas well as damage to the neighboring abdominal aorta. Another factor isthat the filter must be collapsible to a sufficiently small size to beeasily maneuvered and atraumatically advanced intravascularly to theinferior vena cava or other target vessel. Thirdly, the filter shoulddirect the blood clots to the center of the vessel to improvedissolution of the clot within the vessel by the blood flow.

It would be advantageous to provide a vein filter that satisfies theforegoing parameters. Namely, such vein filter would advantageously havesufficient anchoring force to retain the filter within the vessel whileproviding atraumatic contact with the vessel wall, would have aminimized insertion (collapsed) profile to facilitate delivery throughthe vascular system to the surgical site, and would enable migration ofthe captured blood clots to the center of the vessel. Moreover, it wouldalso be advantageous to provide a filter that could simplify insertionthrough the femoral or the right jugular vein or arm into the inferiorvena cava.

Additionally, the need for a vein filter in many patients is temporary.In these instances it would be advantageous to provide a vein filterthat satisfies the foregoing factors and in addition could be readilyremoved from the patient. Thus, the filter would advantageously havestructure to provide sufficient anchoring while enabling atraumaticremoval from the vessel. It would further be advantageous if the filtercould be removed minimally invasively, e.g. intravascularly.

Filters that are temporary are typically removed by a retrieval snarewhich pulls the filter into a retrieval sheath. It would be advantageousto provide a filter which facilitates grasping by the snare as well asfacilitates withdrawal by providing a smooth transition into a retrievalsheath.

SUMMARY

The present invention overcomes the problems and deficiencies of theprior art. The present invention provides a vessel filter movablebetween a collapsed position for delivery to the vessel and an expandedposition for placement within the vessel. A first region of the filterhas a filter portion having a converging region at a first end portionto direct particles toward the center of the filter and the secondregion is flared in the expanded position to have a transverse dimensionincreasing toward a second end portion opposite the first end portion.The second region includes a vessel engaging portion at the second endportion, and includes a plurality of spaced apart struts with adjacentstruts being joined.

The filter is preferably formed from a laser cut tube and composed ofshape memory material. Preferably, the adjacent struts are joined by twoconnecting struts with each of the two connecting struts extendinginwardly toward the other connecting strut to form a substantiallyV-shaped configuration.

The vessel filter can include a plurality of vessel engaging memberswith pointed ends extending from the struts to engage the vessel wall toincrease retention. In one embodiment, one or more of the plurality ofspaced apart struts terminates in vessel engaging hooks.

The filter can include the plurality of spaced apart struts dividing atan end portion to form two connecting struts which extend away from eachother, wherein each connecting strut extends toward a connecting strutof an adjacent strut. In one embodiment, the connecting strut ofadjacent struts are joined at an intermediate region and further extendaway from each other to join the connecting strut emanating from thesame strut. In one embodiment, the connecting struts form a closed ovallike region.

In one embodiment, the filter includes at the first end portion multiplerecesses axially spaced from one another and configured to receive aremoving instrument to remove the filter.

The present invention also provides a vessel filter comprising a firstregion and a second region and movable between a collapsed position fordelivery to the vessel and an expanded position for placement within thevessel. The filter is substantially bell-shaped in the expandedposition. The first region of the filter has a filter portion having aconverging region at a first end portion and the second region has amounting portion for mounting the vessel filter within the vessel. Themounting portion includes a flared region. The second region includes aplurality of struts extending from the filter portion and dividing intooppositely directed struts at a first end and then converging with anoppositely directed strut of an adjacent strut.

The mounting portion can include vessel engaging members to enhanceretention of the filter. In one embodiment, one or more of the pluralityof struts terminates in vessel engaging hooks.

In one embodiment, oppositely directed struts emanating from the strutare rejoined to each other at a second end.

In another aspect of the present invention, a vessel filter is providedcomprising a first region including a filtering section for capturingparticles and having a first transverse dimension and a second regionincluding a mounting section for mounting the filter within the vessel.The mounting section has a second transverse dimension greater than thefirst transverse dimension and includes vessel engaging structure toretain the filter. The first region further includes a plurality ofcutouts configured to receive a removal tool such as a retrieval snareto remove the filter from the vessel, the cutouts being axially spaced.In one embodiment the cutouts are helically formed.

The present invention also provides a vessel filter comprising a firstregion including a filtering section for capturing particles and havinga first transverse dimension and a second region including a mountingsection for mounting the filter within the vessel. The mounting sectionhas a second transverse dimension greater than the first transversedimension and includes vessel engaging structure to retain the filter.The first region further includes a retrieval region including a hookhaving a cutout exposing an internal annular surface dimensioned toreceive a portion of a snare sheath.

Preferably, the retrieval region includes a radiused region having firstand second curved surfaces extending distally and inwardly.

The present invention also provides a vessel filter comprising a firstregion and a second region. The first region includes a filteringsection for capturing particles and having a first transverse dimensionand the second region includes a mounting section for mounting thefilter within the vessel. The mounting section has a second transversedimension greater than the first transverse dimension and includesvessel engaging structure to retain the filter. The first region furtherincludes a retrieval region including a hook at a proximal end thereofand a curved wall spaced axially from the hook to provide a cammingsurface to facilitate entry into a retrieval sheath.

The present invention also provides a vessel filter comprising a firstregion including a filtering section for capturing particles and havinga first transverse dimension and a second region including a mountingsection for mounting the filter within the vessel. The mounting sectionhas a second transverse dimension greater than the first transversedimension and includes vessel engaging structure to retain the filter.The vessel engaging structure includes a first set of hooks and a secondset of hooks, wherein each set of hooks is positioned at an end of themounting section. The first set of hooks has a transverse dimensiongreater than a transverse dimension of the second set of hooks.

Preferably, the mounting section includes a plurality of struts and oneof the hooks extends from each of the struts. Preferably, an end portionof each strut defines a plane and each hook extending from the strutlies in the plane of the strut. In a preferred embodiment, the first setof struts is axially offset from the second set of struts. In apreferred embodiment the filter is formed from a laser cut tube, cut toform a set of struts, wherein each of the hooks of the second set ofhooks is formed of a transverse dimension substantially corresponding toa dimension of one strut and each of the hooks of the first set isformed of a transverse dimension substantially corresponding to adimension of two adjacent struts.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiment(s) of the present disclosure are described hereinwith reference to the drawings wherein:

FIG. 1 is a perspective view of a first embodiment of the vein filter ofthe present invention in the collapsed configuration;

FIG. 2 is an enlarged side view of a portion of the vein filter of FIG.1;

FIG. 3 is a perspective view of the vein filter of FIG. 1 in an expandedconfiguration;

FIG. 4A is a side view of the vein filter of FIG. 1 in another expandedconfiguration;

FIG. 4B is a front view of the vein filter of FIG. 4 in the expandedconfiguration;

FIG. 5 is a side view of the vein filter of FIG. 3 in the expandedconfiguration;

FIG. 6A is a close up view of a portion of the struts showing oneembodiment of anchoring elements having pointed ends;

FIG. 6B is a close up view of a portion of one of the struts showinganother embodiment of anchoring elements in the form of hemisphericalcutouts;

FIG. 7 is a perspective view of an alternate embodiment of the veinfilter of the present invention shown in the expanded configuration;

FIG. 8 is a side view of the vein filter of FIG. 7;

FIG. 9 is a side view of a portion of the vein filter of FIG. 7 shown inthe collapsed configuration;

FIG. 10 is a perspective view of another alternate embodiment of thevein filter of the present invention shown in the expandedconfiguration;

FIG. 11A is a perspective view of yet another alternate embodiment ofthe vein filter of the present invention shown in the expandedconfiguration;

FIG. 11B is a view similar to FIG. 11A showing an alternate embodimentof the hooks;

FIG. 11C is a view similar to FIG. 11A showing another alternateembodiment of the hooks;

FIG. 11D is a view similar to FIG. 11A showing yet another alternateembodiment of the filter of the present invention;

FIG. 11E is a perspective view of the filter of FIG. 11D in thecollapsed position;

FIG. 11F is an enlarged view of the retention hooks of FIG. 11D;

FIG. 11G is a perspective view of an alternate embodiment of the filterof FIG. 7 having the retention hooks of FIG. 11D;

FIG. 11H is an enlarged view of the retention hooks of FIG. 11G in thecollapsed position;

FIG. 12A is a close up perspective view of an alternate embodiment of anend of the filter having a series of cutouts to receive a retrievalsnare;

FIG. 12B is a close up perspective view of an alternate embodiment of anend of the filter having cutouts to receive a retrieval snare;

FIG. 12C is a side view of the embodiment of FIG. 12B showing aretrieval snare placed in one of the cutouts between the coils;

FIG. 13A is a close up perspective view of another alternate embodimentof an end of the filter having a hook to receive a retrieval snare;

FIG. 13B is a view similar to FIG. 13A showing another alternateembodiment of the hook to receive a retrieval snare;

FIGS. 13C and 13D are perspective and top views, respectively, of analternate embodiment of the hook to receive a retrieval snare;

FIG. 13E is an alternate embodiment of the hook of FIG. 13C;

FIGS. 13F and 13G are perspective and side views, respectively, ofanother alternate embodiment of the hook to receive a retrieval snare;

FIGS. 13H-13J are side views showing the method steps for engaging thehook of FIG. 13F for removing the filter utilizing a retrieval snarewhen the snare approaches from one orientation;

FIGS. 13K-13N are side views showing the method steps for engaging thehook of FIG. 13F for removing the filter utilizing a retrieval snarewhen the snare approaches from an orientation opposite the orientationof FIG. 13H;

FIGS. 14, 15 and 16 illustrate delivery and placement of the vesselfilter of FIG. 1 in the inferior vena cava wherein FIG. 14 illustratesinitial insertion of the delivery sheath through the femoral vein, FIG.15 illustrates the delivery sheath being advanced toward the inferiorvena cava just below (upstream) the juncture of the renal arteries; andFIG. 16 illustrates the delivery sheath fully withdrawn to place thefilter in the expanded placement configuration in the inferior venacava;

FIG. 17 is a perspective view of one embodiment of a delivery system forthe vein filter;

FIG. 18 is an exploded view of the delivery system of FIG. 17; and

FIG. 19 is a cross-sectional view showing the engagement of theinterlocking rails of the cartridge with the hub.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawings, wherein like reference numerals identifysimilar or like components throughout the several views, the vein filterof the present invention is described for placement within the inferiorvena cava to capture blood clots or other particles which couldotherwise pass to the lungs.

The filter is movable from a low profile collapsed configuration tofacilitate insertion through the delivery sheath to a larger expandedplacement configuration to enable atraumatic engagement with the vesselwalls to secure (mount) the filter within the inferior vena cava. Thefilter is substantially bell-shaped and has a flared region(portion/section) and a filtering region (portion/section). As describedin more detail below, the filtering portion has inwardly directedstruts, terminating in a converging region, thereby directing particlestoward the central axis of the filter. By directing the particles to thecenter, they will be exposed to greater blood flow which improvesdissolution of the particles. The other portion increases in transversedimension to form a flared region. The flare provides less contact areathan a straight region, resulting in less tissue ingrowth to facilitateremoval of the filter if desired. The flare also reduces the chance ofvessel distortion if inserted into a curved vena cava.

Turning now to details of the filter of the present invention and withinitial reference to FIGS. 1 and 2, the filter is designated generallyby reference numeral 10 and is shown in a collapsed configuration fordelivery. Filter 10 is preferably formed from a single tube 11. In apreferred embodiment, the filter 10 is composed of shape memorymaterial, such as Nitinol, a nickel titanium alloy, or elgiloy however,other materials such as stainless steel are also contemplated. Aplurality of cutouts 12 are formed in the filter 10, preferably by lasercutting although other techniques are contemplated. In the illustratedembodiment, six elongated cutouts are formed, creating six strips orstruts 14 of substantially uniform width separated by the cutouts 12 andextending from tubular portion 18.

The collapsed configuration of filter 10 reduces the overall profile tofacilitate delivery to the site. The diameter of filter 10 in thecollapsed configuration is represented by reference D1 and preferably isabout 2 mm and more preferably about 1.7 mm. Other dimensions are alsocontemplated. The diameter or transverse dimensions of the filter in theexpanded placement configurations (e.g. FIGS. 4A and 5) is greater thanthe diameter or transverse dimension D1 in the collapsed (delivery)configuration. The filter is thus preferably dimensioned for insertionthrough a 6 French delivery system and through a 6 French catheter.

FIGS. 3-5 illustrate the expanded placement configuration of the filter10. Filter 10 is generally bell-shaped in configuration. Filter 10 has aflared region 17 and a converging region 21 at the filtering section 19.In larger vessels, the filter can expand to a diameter D2 shown in FIG.5. In smaller vessels, the filter expands to a smaller diameter, e.g.D3, shown in FIG. 4. Diameters (or transverse dimensions) D2-D3preferably range from about 18 mm to about 32 mm, depending on theinternal diameter of the vessel wall as will be explained in more detailbelow. Other dimensions are also contemplated.

The elongated struts 14 are spaced apart as shown and extend at an angleaway from the longitudinal axis L of filter 10 in region 17 to provide aflare. Preferably, this angle or taper is about 10°, although otherdimensions are contemplated. In the filtering region 19, beginning at anintermediate portion of the filter (the transition between the first andsecond regions 17, 19) the struts 14 curve or bend inwardly (region 23)toward the longitudinal axis and then extend inwardly at an angle to thetubular portion 18, thereby forming an angle with the longitudinal axis.In the illustrated embodiment, when expanded, the six struts 14 areshown spaced approximately 60 degrees apart. It is also contemplatedthat a fewer or greater number of struts could be provided and spacingother than 60 degrees be provided.

In the expanded placement configuration, a portion of the each elongatedstrut 14 has an outer surface 20 for engagement with the vessel wall toretain the filter 10 in position in the vessel. This region is angledwith respect to the longitudinal axis. The outer surface 20 of struts 14could be roughened to enhance engagement. Alternatively, a plurality ofatraumatic tabs, barbs or other penetrating members can extend from theouter surface 20 of the struts 14 to engage the vessel wall to retainthe filter. FIGS. 6A and 6B show examples of such retention features. InFIG. 6B, the filter has a series of hemispherical cutouts 152 formedalong the length of the struts 154 forming pointed edges 156 to engagethe vessel wall. The cutouts 152 can be formed along the length of thestrut 154 or alternatively be formed only along a portion of the length.The cutouts can also be formed on fewer than all the struts.

In the embodiment of FIG. 6A, the filter has anchoring elements 162formed by cutouts 163 at the ends of the struts 164. Anchoring elements162 have pointed ends 165. In the collapsed configuration the anchoringelements 162 and their pointed ends 165 are aligned with the struts 164,substantially parallel with the longitudinal axis of the filter tomaintain a reduced profile. When the filter moves to the expandedconfiguration, the pointed ends 165 face outwardly as shown in FIG. 6A.Anchoring elements 162 can be placed in the end regions of the strut orin other locations. The anchoring elements can also be placed in theopposite direction shown.

In the embodiment of FIG. 11A, the struts 174 of filter 170 terminate inhooks 172 which extend substantially perpendicular from the strut. Hooksextend from the substantially V-shaped region 179 formed by the joiningof connecting struts 174 a, 174 b. In the alternate embodiment of FIG.11C, struts 184 of filter 180 also terminate in substantiallyperpendicular hooks 182, however this arrangement is achieved bytorquing the connecting struts 184 a, 184 b at the curved region 185 sothe hooks bend out of the plane. As shown, hooks 182 extend fromV-shaped region 189 formed by the connecting struts 184 a, 184 b. In thealternate embodiment of FIG. 11B, the hooks 192 of filter 190 (havingstruts 194) lie in the plane of the connecting struts 194 a, 194 b,flush with the wide width surface “w” of the V-shaped region 199 ofconnecting struts 194 a, 194 b.

In the alternate embodiment of FIGS. 11D-11 F, the hooks 302 lie in thesame plane as the connecting struts 304 a, 304B of struts 310 as in FIG.11 B; however the hooks of filter 301 are of two different sizes. Morespecifically, hooks 302 a are larger than hooks 302 b and struts 310 areseparated by cutouts 312. Preferably when formed in a laser cut tube,hooks 302 a are formed so that they occupy a region equivalent to thetransverse dimension of two adjacent struts. For example, in thecollapsed configuration, hook 302 a occupies a region (dimension) offour connecting struts while smaller hook 302 b would only occupy theregion (dimension) of two connecting struts. Smaller hooks 302 b arespaced axially inwardly with respect to larger hooks 302 a to minimizethe collapsed profile (transverse dimension) of the filter whencollapsed for insertion. In this preferred embodiment, smaller hooks 302b occupy the space created by the larger hooks 302 a so they can beconsidered as nesting within larger hooks 306 a. Stated another way,each hook 302 b has an outer surface 307 which conforms (follows thecontour) to an inner surface 309 of a hook 306 a. The penetrating tips306 a, 306 b in hooks 302 a, 302 b, respectively, penetrate the tissueto retain the filter, preferably temporarily.

The aforedescribed hooks 172, 182, 192, 302 can be used with any of thedisclosed embodiments (see e.g. FIG. 11G). Such hooks can also be formedor placed on fewer than all the struts.

Referring back to FIGS. 3-5, the filter portion of filter 10 will now bediscussed. As noted above, the filtering section of filter 10 at a firstend of the filter is designated generally by reference numeral 19 andincludes the converging region 21. Filtering section 19 extends from theflared region 17, and extends toward the central longitudinal axis L ofthe filter 10 and converges at portion 32 into tubular portion 18. Atthe transition region between the filtering and flared regions 19, 17,struts 14 bend inwardly (region 23), then extend radially inwardlytoward the tubular portion 18, and transition to the tubular portion 18.The tubular portion 18 and converging region 19 of the filter 10 arespaced both axially outwardly and radially inwardly from the bendregions 23 of the strut 14. (Axially outwardly is represented by arrow“a” and radially inwardly is represented by arrow “b” in FIG. 4A). Thefilter is designed to direct particles to the center of the filter andvessel. (Trapping the particles at the center rather than the edges ofthe filter is more desirable because there is less blood flow at theedges of the vessel and greater blood flow at the center to betterdissolve the particles.) For clarity, not all of these sections of eachstrut 14 are labeled in the drawings, it being understood that thenon-labeled struts can have the same configurations.

Turning now to the flared region 17, each strut 14 is divided into twoconnecting strut portions 14 a, 14 b. Preferably, each strut portion 14a, 14 b is about one half the width of the undivided strut 14, althoughother widths are contemplated. The strut portions 14 a, 14 b of eachdivided strut 14 extend in opposite directions and include a curvedregion 25 as the strut portions 14 a, 14 b each extend toward respectivestrut portion 14 a or 14 b of an adjacent strut. That is, strut portions14 a, 14 b form connecting portions to connect adjacent struts 14 asconnecting strut 14 a of one strut is connected to connecting strut 14 bof an adjacent strut. Connecting strut portion 14 a on one strut andportion 14 b of another strut converge at end region 29 of the filterand form a substantially V-shaped region. Six such V-shaped end portionsare preferably formed, each portion connecting adjacent struts. Notethat although all six struts 14 are shown interconnected, it is alsocontemplated that fewer than all the struts can be interconnected.

It should be understood that the elongated struts 14 bend as they movefrom their collapsed position to their expanded placement configuration.Their designations of longitudinal, angled, curved, bowed, connected,connecting strut, etc. in the illustrated embodiments refer to the sameintegral strut and are divided into such regions for ease ofunderstanding. Therefore, stated another away, the filter 10 can beviewed as having a filtering section 19 at a first end extending fromthe tubular portion 18. As viewed, each of the struts 14 emerges fromthe tubular portion 18 at an angle that extends outwardly away from thecenter to transition to curved portions 23. The curved portions 23extend outwardly away from the longitudinal axis forming a flare orregion of progressively increasing transverse dimension. In this flaredregion 17, near a second end of the filter (opposite the end containingtubular portion 18), the struts 14 are interconnected by connectingstruts 14 a, 14 b that curve inwardly toward the connecting strut 14 aor 14 b of an adjacent strut to form a substantially V-shaped endportion.

In the placement (expanded) configuration, the filter 10 moves towardsits memorized position and the extent it returns to its fully memorizedposition will be dependent on the size of the vessel in which the filter10 is inserted. (The larger the vessel, the closer the filter comes toreturning to its fully memorized position). This can be understood bycomparing FIGS. 4A and 5 which illustrate by way of example two possibleexpanded dimensions of the filter; FIG. 4A showing expansion to asmaller dimension occurring in smaller diameter vessels and FIG. 5showing expansion to a larger dimension occurring in larger diametervessels.

To enable movement between an expanded and collapsed configuration, thefilter tube of the embodiments described herein is preferably made ofshape memory metal material, such as Nitinol, a nickel titanium alloy.The memorized configuration of the filter 10 is shown in FIG. 1. Tofacilitate passage of the filter 10 through the lumen of the deliverysheath 100 (shown in FIG. 14 in conjunction with the method ofinsertion) and into the vessel, cold saline is injected into thedelivery sheath or catheter 100 and around the filter 10 in itscollapsed position within the delivery sheath 100. This shape memorymaterial characteristically exhibits rigidity in the austenitic stateand more flexibility in the martensitic state. The cold saline maintainsthe temperature dependent filter 10 in a relatively softer condition asit is in the martensitic state within the sheath. This facilitates theexit of filter 10 from the sheath 100 as frictional contact between thefilter 10 and the inner surface of the sheath would otherwise occur ifthe filter was maintained in a rigid, i.e. austenitic, condition.

Once ejected from the delivery sheath or catheter 100, the filter is nolonger cooled and is exposed to the warmer body temperature, whichcauses the filter 10 to return towards its austenitic memorizedconfiguration.

The filter 10 (and other filters described herein) can be insertedthrough the jugular vein in the neck of the patient or through thefemoral vein in the leg of the patient or the arm. The filters can alsobe placed in the superior vena cava.

FIGS. 14-16 illustrate delivery and placement of the filter 10, by wayof example, in the inferior vena cava. Delivery catheter 100 is insertedthrough the femoral vein “f” and advanced through the iliac arteriesinto the inferior vena cava. Delivery catheter would be withdrawn oncethe tip of the sheath is adjacent the structure so that withdrawal ofthe sheath would place the filter in the desired location of FIG. 16.Tubing 104 and valve assembly 106 enable saline injection. Deliverycatheter 100 is withdrawn to enable filter 10 to be warmed by bodytemperature to transition to the expanded placement configuration. Theother filters described herein could be inserted in the same manner.Note it is implanted in the orientation such that filter section 19 isdownstream of the flared section 17. This enables blood clots or otherparticles to be directed to the center of the filter section by theangled struts. Thus the direction of insertion, e.g. upstream ordownstream direction, will determine how the filter is to be positionedin the delivery catheter.

In an alternate embodiment of the filter, the strut width can vary. Forexample, the struts can be wider at the flared region than at thefiltering portion. This is preferably achieved by removing material tocreate the thinner portions. These thinner portions increase theflexibility of the filter for forming the angled and curved portionsupon deployment. Alternatively, the filter can have struts which arethinner, rather than wider, at the flared region, than at the angled andcurved regions of the filtering portion. This would provide morestability at the curved regions. The adjustment of the widths isdesigned to strike a balance between stability and flexibility of thevarious regions of the filter. Thus, other width variations arecontemplated such as making multiple width changes within each strutand/or in different struts.

FIGS. 7-9 illustrate an alternate embodiment of the filter, designatedby reference numeral 110. Filter 110 is similar to filter 10 except forend region 121. That is, like filter 10, filter 110 has a filteringregion 119 which extends from the flared region 117, and extends towardthe central longitudinal axis L of the filter 110 and converges atportion 132 into tubular portion 118. Struts 114 bend inwardly towardthe longitudinal axis of the filter 10 at region 123. For clarity, notall of these sections of each strut 114 are labeled in the drawing, itbeing understood that the non-labeled struts can have the sameconfigurations. The flared region 117 as in filter 10 is of an anglepreferably about 8 degrees although other angles are contemplated.

The end region 121 of filter 110 where the struts 114 interconnectdiffers from filter 10. In filter 110, the struts 114 are interconnectedby connecting strut portions 114 a, 114 b that curve outwardly away fromthe central axis and then inwardly toward each other to form asubstantially V-shaped end portion 127. At the outward curved or bowedportion 124, the connecting struts are joined to connecting struts ofadjacent struts 114 (region 125). Thus, a closed geometric shape 133 isformed as shown. The closed shape as shown is substantially oval inconfiguration, although other shapes are contemplated. Six such closedgeometric shapes are preferably formed, each connecting adjacent struts,although fewer closed shapes are contemplated if fewer than all thestruts are interconnected. Also, the length of the region 125 where thestruts are joined can be shorter or longer than that shown, therebychanging the configuration of the closed geometric shape (e.g. making itlonger or shorter).

Stated in other words, each strut 114 divides into two connecting strutportions 114 a, 114 b which initially extend outwardly from each other.As each strut extends outwardly, the strut portion 114 a joins the strutportion 114 b of an adjacent strut at region 125. After this joinedregion 125, the strut portions 114 a and 114 b which emanate from thesame strut extend inwardly towards each other and are joined at theirends into a substantially V-shaped end, designated by reference numeral127.

The collapsed configuration of filter 110 is shown in FIG. 9 withcutouts 112 forming six struts 114. Regions 113 illustrate where struts114 divide.

In the alternate embodiment of FIG. 10, filter 150 resembles filter 10of FIG. 1 except for the additional connecting struts or ribs 152. Theseribs increase the stability of the filter 150. As shown, the two ribs152 extend from adjacent struts 154 and curve inwardly towards eachother and are joined at region 156 (forming a V-like connection). Theribs 152 can be arranged so they are axially aligned as in FIG. 10 oralternatively can be staggered, i.e. spaced axially (not shown). Also,the ribs can be placed between fewer than all the struts and the ribscan be utilized with any of the foregoing embodiments. Note that theribs are preferably integrally formed with the filter, formed by thelaser cutting process mentioned above; however, alternatively the ribscan be attached to the struts. Struts 154 divide into connecting struts154 a, 154 b in the embodiment of FIG. 1.

FIGS. 11G and 11H illustrate an alternate embodiment of the filter ofFIG. 7 having the hooks of filter 301 of FIG. 11D. Filter 350, likefilter 110, has struts 354 which are interconnected by connecting strutportions 354 a, 354 b that curve outwardly then inwardly toward eachother to form V-shaped portions 357, terminating in hooks 356. As inFIG. 11D, large hooks 356 a alternate with axially offset smaller hooks356 b and are identical to hooks 306 a, 306 b of FIG. 11D.

In another embodiment, the ribs could curve radially outward near theirtips, thus contacting the vessel wall and acting as a retainingmechanism.

The foregoing filters can be inserted through the femoral vein oralternatively through the internal jugular vein. It can be removed fromaccess through the internal jugular vein or femoral vein. Variousmethods can be used to remove the filter such as those described incommonly assigned co-pending application Ser. No. 09/911,097, filed Jul.23, 2001, now published application 2002-0193827-A1, published Dec. 19,2001, the entire contents of which is incorporated herein by reference,including for example, slotted hooks, graspers, etc. A recess or cutoutcan also be provided at the tubular end portions to receive a snare orother device for removal. A hook 222 at tubular portion 220 isillustrated in the embodiment of FIG. 13A and is configured to receive asnare. FIG. 13B illustrates another embodiment of a hook. Hook 232formed in tubular portion 230 forms a cutout 234 for receiving a snareor other removal device. The snare can surround and grasp both ears 235.However, the gap 237 between the ears 235 also enables a retrieval snareto lie in the gap 237 to surround and grasp one of the two ears 235.

In the alternate embodiment of FIGS. 13C and 13D, hook 272 is similar tohook 232 of FIG. 13B in that it has two ears 275 with a gap 277therebetween. However it differs in that it has a bottom cutout 278formed between walls 279. It also differs in that surfaces 274 of ears275 are rounded and outer proximal walls 278 a angle outwardly(proximally) to curved peak 276 then angle inwardly (wall 278 b) toprovide a smoother transition into the retrieval sheath. Thus, twoangled transitions are provided.

In the alternate embodiment of FIG. 13E, to further enhance thetransition to facilitate withdrawal into the retrieval sheath, the sidewalls 284 extending into ears 285 of hook 282 angle inwardly toward thelongitudinal axis. Consequently, there are three angled transitions: 1)an angled transition in a first direction formed by angled walls 288 awhich angle proximally outwardly from the edge 285 a of ears 285 to thecurved peak 285 b (the proximal end of the hook is designated generallyby reference numeral 283); 2) an angled transition in a second directionformed by angled walls 288 b which angle distally outwardly from curvedpeak 285 b; and 3) an angled transition formed by walls 284 which angleproximally inwardly as walls 284 come closer together toward theproximal end. This results in a smoother transition into the retrievalsheath as it reduces the likelihood of the filter proximal end, i.e. thehook, being caught on the edge of the sheath—the angled edges whichcreate camming surface for all approaches of the filter (360 degreerange) will help the hook edges slide into the sheath.

FIGS. 13F and 13G illustrate another alternate embodiment of theretrieval hook of the present invention. This is the retrieval hookshown in conjunction with filter 301 of the embodiment of FIGS. 11 D and11G. Hook 290 has a curved hook 292 at the proximalmost end. This hook292 is configured to receive a retrieval snare or other retrievaldevice. A portion of the wall of the hook 290 is cut out to expose theannular interior surface 294. That is, being formed from a laser cuttube, a wall portion is removed to expose curved inner wall surface 294.This annular interior surface 294 extends from radiused region 295 toproximalmost edge 296. The interior surface 294, for ease ofexplanation, can be considered to have an interior surface 294 a at theradiused region 295 and an interior surface 294 b at the hook 292. Theinterior surface 294 b accommodates a portion of a tubular snare sheath.That is, the outer wall of the snare sheath (tube) can partially fitwithin the cut out region 293. This enhances removal as the snare pullsthe filter hook into collinear arrangement with the sheath tube. Thiscan be appreciated by reference to FIGS. 13H-13J discussed below. Theradiused region 295, spaced axially (distal) from the hook 292, includesa radiused or curved edge defined by radiused side walls 297 a, 297 cand top wall 297 b. The angled side walls 297 a, 297 c form cammingsurfaces to direct the hook 290 and filter into the retrieval sheath.This can be appreciated by reference to FIGS. 13K-13N discussed below.

It should be appreciated, that the hook can be formed in other ways toprovide an interior annular surface to function in a similar manner assurface 294, i.e. to receive the snare tube.

It should be appreciated that any of the retrieval hooks can be usedwith any of the filters described herein.

In FIGS. 13H-13J, the snare approaches the retrieval hook 290 in theorientation shown. This results in a collinear arrangement. Morespecifically, the snare 502 is part of a retrieval system which includesa snare sheath or tube 504 through which the snare 502 extends. Thedistal wall 503 of snare sheath 504 provides for cinching of the snare502. The snare sheath 504 is inserted through retrieval sheath 510. Whenthe filter is pulled into the retrieval sheath 510 it is collapsed forremoval. As discussed above, preferably cold saline is injected duringthe removal process to cool the sheath to transition to a softermartensitic state to facilitate removal.

In the orientation shown, as snare 502 retracts the filter, the snaresheath 504 fits into the cut out region 293 as its outer wall conformsto the inner wall surface 294 b of hook 292. Thus, the hook 290 andsnare sheath 504 become substantially collinear as shown in FIG. 13I.This collinear arrangement facilitates retraction into the retrievalsheath 510 as it reduces the likelihood of a wall of the hook gettingcaught on the distal edge 512 of the retrieval sheath 510, thusproviding a smoother transition into the sheath as shown in FIG. 13J.

FIGS. 13K-13N illustrate the retrieval steps when the snare approachesfrom the opposite orientation of FIG. 13H, i.e. below the hook as viewedin the orientation of FIG. 13K. As the snare 502 retracts the filtertowards the sheath 510, the wall 297 b contacts the edge 512 ofretrieval sheath 510 and due to the radiused walls 297 a, 297 c(depending on the side of contact), the hook is cammed downwardly (inthe orientation of FIG. 13M) into the retrieval sheath 510 as shown inFIG. 13N. This provides a smooth transition into the retrieval sheath510 as it reduces the likelihood of the hook being caught on the sheathedge.

FIG. 12A illustrates another embodiment having a series of recesses 210along the length of the tubular portion 212. This enables the tubularportion 212 to be grasped at several locations along its length,facilitating grasping of the filter for removal. These multiple recessesor cutouts 210 are axially spaced as shown. In the embodiment of FIG.12B, the end of the tubular portion 240 has a series of axially spacedcutouts 242 which form a coil-like engagement structure. This engagementstructure provides multiple engagement areas for a retrieval (removal)device, such as a retrieval snare, for grasping the filter as the devicecan for instance be cinched in any of the spaces (formed by the cutouts)between the turns 246 in the helical coil. FIG. 12C shows a snare 300placed in one of the cutouts 242.

To facilitate removal of the filter from the vessel, cold saline can beinjected onto the implanted filter to change the temperature of thefilter to move it to a relatively softer condition to facilitate thefilter being drawn in to the retrieval sheath. That is, injection ofcold saline will cause the filter to approach its martensitic state,bringing the filter to a more flexible condition. The flexible conditionfacilitates the collapse and withdrawal of the filter into the retrievalsheath, by decreasing the frictional contact between the filter and theinner surface of the retrieval sheath.

A delivery system for the filter of the present invention is shown inFIGS. 17 and 18. The delivery system 600 includes a hub 602, a cartridge604 containing the filter, a pusher 606 and a wire 608 extending throughthe pusher 606. The wire 608 extends through the cartridge 604 andthrough the length of tube 603 to maintain a separation of the hooks,e.g. hooks 402 of filter 350 of FIG. 11G, during insertion of thedelivery system and delivery of the filter. The cartridge 604 isremovably attached to the hub 602, preferably by a snap-fit althoughother modes of attachment are also contemplated. The cartridgepreferably has markings (not shown) on the outer surface to indicate afemoral or jugular direction so the user knows the orientation to attachthe cartridge 604 to hub 602.

Once attached, advancement of the pusher 604 advances the filter fromthe cartridge and through tube 603 as the distal edge of the pusher 604abuts the proximal end of the filter, with the wire 608 (e.g., a Nitinolwire) preventing entanglement of the retention hooks. The wire 608 alsoprovides support (stability) for the pusher 604 as the pusher 604 isadvanced over the wire 608. The filter is forced out of the distal endof the tube, where it is no longer cooled by saline and is warmed bybody temperature to return toward its memorized configuration.

To enhance the retention of the cartridge 604 in the hub 602, a lockingmechanism can be provided such as the mechanism of FIG. 19. Thecartridge 604 has a pair of locking rails 612 a, 612 b, each including arespective recess 614 a, 614 b. The hub 602 contains a detent 620 asshown. When the cartridge 604 is inserted into the hub 602, the recess614 a of the locking rails 612 a is retained by the detent 620. Thislocks the cartridge 604 to the hub 602 during use, preventing unwantedseparation of the cartridge 604 from the hub 602. If access via thejugular artery instead of the femoral artery is desired, then thecartridge is inserted so that recess 614 b of rail 612 b engages detent620 of hub 602.

While the above description contains many specifics, those specificsshould not be construed as limitations on the scope of the disclosure,but merely as exemplifications of preferred embodiments thereof. Forexample, the filters can be inserted in other regions of the body. Also,any of the aforedescribed filters can have mounting sections of varyingthickness. The foregoing filters can be made of materials other thanshape memory material. Those skilled in the art will envision many otherpossible variations that are within the scope and spirit of thedisclosure as defined by the claims appended hereto.

1. A vessel filter comprising a first region and a second region and amidpoint defined on a longitudinal axis of the filter and defined as apoint equidistant from a proximalmost end of the filter and a distalmostend of the filter, the filter movable between a collapsed position fordelivery to a vessel and an expanded position for placement within thevessel, the first region having a filter portion having a convergingregion at a first end portion to direct particles toward a center of thefilter, the first region including a plurality of struts extendinglongitudinally through the first region and being unconnected proximalof the midpoint such that the struts are unconnected between theconverging region and the midpoint, the second region being flared inthe expanded position to have a transverse dimension increasing toward asecond end portion opposite the first end portion, the second regionincluding a vessel engaging portion at the second end portion andincluding a plurality of spaced apart struts with adjacent struts beingjoined distal of the midpoint, the adjacent struts joined at a terminalend of the second end portion to thereby join a distal end of thestruts, wherein the struts in the second region distal of the centerdivide widthwise at an end portion to form two connecting struts whichextend away from each other, each connecting strut extending toward aconnecting strut of an adjacent strut, and vessel engaging hooks at theterminal end of the second end portion to secure the filter within thevessel.
 2. The vessel filter of claim 1, wherein the adjacent struts arejoined by the two connecting struts, each of the two connecting strutsextending inwardly toward the other connecting strut.
 3. The vesselfilter of claim 2, wherein the connecting struts converge at their endsto form a substantially V-shaped configuration.
 4. The vessel filter ofclaim 1, wherein the connecting struts of adjacent struts are joined atan intermediate region and further extend away from each other to jointhe connecting strut emanating from the same strut.
 5. The vessel filterof claim 4, wherein the connecting struts form a closed oval likeregion.
 6. The vessel filter of claim 1, wherein the filter is formedfrom a laser cut tube and composed of shape memory material.
 7. Thevessel filter of claim 1, wherein the filter includes at the first endportion multiple recesses axially spaced from one another and configuredto receive a removing instrument to remove the filter.
 8. The vesselfilter of claim 1, the connecting struts initially extend away from eachother and then extend towards one another, forming a closed geometricconfiguration.
 9. A vessel filter comprising a first proximal region ata first end of the filter and a second region at a second opposite endof the filter and a midpoint defined as a point equidistant from aproximalmost end of the filter and a distalmost end of the filter, thesecond end of the filter having a transverse dimension greater than atransverse dimension of the first end, the filter being movable betweena collapsed position for delivery to a vessel and an expanded positionfor placement within the vessel, the filter being substantiallybell-shaped in the expanded position, the first region of the filterhaving a filter portion having a converging region at a first endportion, the second region of the filter having a mounting portion formounting the vessel filter within the vessel, the mounting portionincluding a flared region extending along a length of the filter whereinthe second region includes a plurality of struts, the struts extendinglongitudinally through the midpoint and the second region, the strutshaving a first widthwise dimension defined along a length of the strutthrough the midpoint and the second region and dividing at a first endinto oppositely directed struts of a second widthwise dimension smallerthan the first widthwise dimension and then converging with anoppositely directed strut of an adjacent strut, the struts dividing onlyat a region distal of the midpoint and adjacent struts extending fromthe converging region being unconnected between the converging regionand the midpoint.
 10. The vessel filter of claim 9, wherein the mountingportion includes vessel engaging members to enhance retention of thefilter.
 11. The vessel filter of claim 9, wherein oppositely directedstruts emanating from one of the plurality of struts are rejoined toeach other at a second end.
 12. The vessel filter of claim 9, whereinone or more of the struts terminates in vessel engaging hooks.